52 
Psyche 
[March 
different matter. In the orthopteroids, as noted above, the media 
does not show the clear division into a convex anterior branch and 
a concave posterior one. It is often deeply forked and the posterior 
branch may be strongly concave or only slightly concave or even 
neutral (flat), but I think it can be safely said that there is no 
orthopteroid known in which the anterior branch of the media is 
convex. We have no way of knowing, therefore, whether in such 
cases the entire media consists only of MP (with a flattened anterior 
branch) or of MA and MP, with a flattened MA. The only positive 
criterion by which we can identify a vein in the orthopteroids as 
homologous with MA of the Palaeoptera is by its convexity — which 
none have. I think there is enough evidence, however, to justify the 
probable determination of the anterior branch of M as MA in some 
families of orthopteroids, but the determination is only a working 
hypothesis. 5 
Another area of controversy is the relationship between CuA and 
M. In the majority of the orthopteroids there is some type of con- 
nection between M and CuA, if only a short cross-vein. In others 
(as Stereopteridae, figures 10-13 of the present paper), CuA curves 
upwards and fuses with part of M before diverging off as an in- 
dependent vein. It should be noted that there is marked individual 
variation in the nature and amount of this coalescence. In others, 
such as the Blattinopsidae, there is a strongly convex stem of M 
(see figures 7 and 8 of this paper) which become abruptly flat or 
concave after the divergence of a short, convex, posterior branch. I 
think it probable here that the anterior branch of CuA is fused with 
M from the very base until the point of divergence. A somewhat 
similar situation appears to occur in the Oedischiidae and related 
families (these being treated here as true Orthoptera), but I believe 
the homologies are different (see figure 15). The stem of M, in- 
stead of being markedly convex, is flat or even concave. The short 
vein which diverges towards CuA is rather weak in the Oedischiidae, 
although it may be stronger in other, related families. In this case, 
5 In my own descriptive accounts of the Paleozoic orthopteroids I use the 
designation MA and MP if the posterior branch is definitely concave and 
the anterior branch flat; if the posterior branch is flat like the anterior 
one I use the designation M for the entire system; if all branches of the 
media are concave, I use the designation MP for all. 
Explanation of Plate 4 
Lemmatophora typa Sellards. Photograph of specimen No. 3539, Museum 
of Comparative Zoology, showing prothoracic lobes, with hair covering and 
reticulated pattern. Original. 
